An AC surface discharge panel as a typical plasma display panel (hereinafter, abbreviated as a “panel”) includes a front panel and a rear panel disposed facing each other with a large number of discharge cells provided therebetween. The front panel has a plurality of display electrodes, each composed of a pair of scan electrode and sustain electrode, formed in parallel to each other on a glass front substrate. A dielectric layer and a protective layer are formed so as to cover the display electrode pairs. The rear panel includes a plurality of data electrodes formed in parallel on a rear glass substrate, a dielectric layer formed so as to cover the data electrodes, and further, a plurality of barrier ribs formed in parallel to the data electrodes on the dielectric layer. A phosphor layer is formed on the top surface of the dielectric layer and the side surface of the barrier ribs. The front panel and the rear panel are disposed facing each other so that the display electrodes three-dimensionally intersect with the data electrodes, and sealed to each other. The discharge space inside thereof is filled with a discharge gas. Herein, a discharge cell is formed in a portion where the display electrode and the data electrode face each other. In a panel having such a configuration, ultraviolet light is generated by gas discharge in each discharge cell, and this ultraviolet light excites a phosphor for each color of RGB to cause light emission for color display.
As a method for driving a panel, a subfield method is generally employed. The subfield method divides one field period into a plurality of subfields, and carries out gradation display by a combination of subfields to emit light. Each subfield includes an initializing period, an address period, and a sustain period. In the initializing period, an initializing voltage is applied to each electrode so as to form wall charge necessary for a subsequent address operation. In the address period, a scanning pulse is applied to the scan electrode, and an address pulse is applied to the data electrode, thus generating address discharge in a discharge cell to be displayed. In the sustain period, a sustain pulse is applied alternately to the scan electrode and the sustain electrode so as to cause sustain discharge in a discharge cell in which address discharge has been generated. Thus, a phosphor layer of the corresponding discharge cell is allowed to emit light so as to carry out an image display.
Thus, the plasma display device includes a drive circuit for each electrode to drive each electrode of the panel. These electrode drive circuits include a large number of switching elements. In particular, a scan electrode drive circuit for driving the scan electrode needs to generate complicated drive waveforms, and configured by combining an initializing voltage generating circuit, a sustain pulse generating circuit, a scan pulse generating circuit, and the like. In order to avoid interference between these circuits, a separation switch is provided between these circuits if necessary (see, for example, patent document 1).
However, when such a separation switch is provided in an electric current passage, the output impedance of the scan electrode drive circuit is increased, causing a large electric power loss accompanying sustain discharge. Furthermore, a large output impedance may be a factor for making discharge unstable, for example, the ringing is superimposed on the sustain pulse due to the resonance of the output impedance and the electrode capacitance and the like, or the value of the voltage drop by the output impedance is dependent upon the amount of electric current, so that a sustain pulse voltage applied to the discharge cell is also dependent upon the amount of electric current. Furthermore, since a high voltage is applied to such separation switches, the separation switch must be configured by using high breakdown voltage switching elements. Since the on-resistance of the high breakdown voltage switching element is high, it is necessary that a large number of switching elements are connected in parallel so as to reduce the output impedance.
In order to solve such problems, a novel scan electrode drive circuit capable of reducing the output impedance of the scan electrode drive circuit and reducing the breakdown voltage of the separation switch has been proposed (see, for example, patent document 2).
With the scan electrode drive circuit described in patent document 2, the breakdown voltage of the separation switch can be reduced, however, the breakdown voltage of switching elements constituting the scan electrode drive circuit other than the separation switching elements is increased, which increases the impedance of such switching elements.    [Patent document 1] Japanese Patent Unexamined Publication No. 2005-266460    [Patent document 2] Japanese Patent Unexamined Publication No. 2006-201735